The demand for PDP display devices using a plasma display panel (PDP) grows as a flat display capable of large-screen displays. The PDP display device includes a plasma display panel, a front panel placed on the front of the plasma display panel, a drive circuit placed on the back of the plasma display panel, a frame containing them, and the like.
On the front substrate scan electrodes extend from, for example, the left-hand end of the front substrate to the display area, while discharge-sustain electrodes extend from, for example, the right-hand end of the front substrate to the display area. On the back substrate, address electrodes each extend in a direction at right angles to the scan electrode and the discharge-sustain electrode. Sub-pixels are respectively formed in positions corresponding to the intersections of the address electrodes with the scan and discharge-sustain electrodes. The sub-pixels are arranged in matrix form in the display area to form an image.
A discharge is initiated between the scan electrode and the discharge-sustain electrode which are formed on the front substrate, to cause a phosphor in each sub-pixel to emit light for generation of an image. In this regard, in general, a voltage of 180V to 190V is applied between the scan electrode and the discharge-sustain electrode in order to initiate a discharge between the scan electrode and the discharge-sustain electrode. Accordingly, a dielectric layer is deposited to cover the scan electrode and the discharge-sustain electrode for preventing dielectric breakdown from occurring between the scan electrode and the discharge-sustain electrode.
For maintaining a low discharge voltage, it is desirable that a substance having a low secondary electron emission coefficient γ exists in the discharge space. Therefore, the surface of the dielectric layer is coated with an approximately 1-μm thick coating of MgO having a high secondary electron emission coefficient γ as a protective film. However, MgO is deliquescent and therefore exposure of it to the air transforms the surface of the protective film, thus making the surface become clouded or decreasing the secondary electron emission coefficient.
A measure to prevent such transformation of the protective film in the air as described above is described in “Patent Literature 1” in which the protective film is temporarily covered with a protective film such as an SiO2 film (hereinafter referred to as “inert film”), and then the inert film is removed around electrodes by generating a discharge after a plasma display panel is completed. On the other hand, “Patent Literature 2” describes the use of SiOx for an inert film in which x is set to a value ranging from 1.3 to 1.9 to improve the barrier properties against oxygen or moisture vapor.    Patent Literature 1: JP Patent 3073451    Patent Literature 2: JP Patent 3563994